1. Field of the Invention
This invention relates to a system for adjusting the position between a waste ejector and a cutting cylinder for material in strip form in a rotary cutting machine, cylinder comprising at least one radial needle for retaining waste and projecting radially from its surface, ejector having a rectilinear part parallel to the generatrix of the cylinder and traversed by at least one slot coinciding with the trajectory of radial needle for the passage thereof.
2. Description of Related Art
When the cardboard waste is separated from a strip during its cutting for the manufacture of folding boxes in particular, on rotary cutting machines, it is essential that the waste should be ejected controllably to prevent it causing any jamming. To this end, one of the two cutting cylinders between which the strip of cardboard is cut comprises radial needles between the cutting fillets, which needles penetrate the waste during a cutting operation and separate it from the strip, entraining it with the cylinder, while the strip moves away from the cylinder following a horizontal trajectory.
This waste must then be extracted from radial needles during rotation of the cylinder in order to free radial needles and enable them to penetrate other waste during their next passage in the cutting zone of the cardboard strip. To this end, ejectors are provided in the form of fixed combs with edges parallel to the cylinder generatrix, cut out so that they can very closely approach the trajectory of the cutting fillets of the cylinder while allowing the radial needles projecting beyond the apices of said cutting fillets to pass. The edges of the ejectors can thus be inserted between the apices of the cutting fillets and the waste and extract the waste from the radial needles when the latter move away from the ejectors following the rotation of the cylinder.
The edges of these combs must be positioned with high precision with respect to the cylinder. If too large a spacing is left between the apices of the cutting fillets and the edges of the combs, there is a risk that the cardboard waste will pass between the comb and the fillet. This may initially result in a deformation of the comb and may also break the radial needle and hence a fillet. The damage increases generally with rotation of the cylinder, until the machine stops. If, on the other hand, the distance is too small, there is a risk that the comb will come into collision with a cutting fillet and also cause damage successively until stoppage of the machine.
Since the comb is subjected to impacts whenever it meets waste, and in view of the very small tolerances allowed for its positioning, it not only has to be positioned with very high accuracy but must also be prevented from vibrating, since otherwise the said two risks can occur more or less simultaneously on different combs.
To guarantee reliable operation of a waste ejector of the type referred to, it must satisfy an extremely strict specification. The positioning of the comb must be possible with a tolerance of not more than xc2x10.02 mm. Its rigidity may not allow a movement in excess of 5 xcexcm, even in response to impacts. The comb must not undergo any torsion irrespective of the axis considered.
To be able to satisfy the above positioning accuracy, there must be an adjustment system. Conventional adjustment systems assume the existence of a guide for each adjustment axis. Consequently, the movable element must be locked on the guide once it has reached the required position,-and this implies a displacement with respect to the desired position, induced by the locking. It is therefore necessary to proceed by repetition and this repetition method which is more or less carried out at random involves the risk that the final precision accepted will be only approximate, together with the danger that implies.
The use of cross-guides with locking, which is well known in machine tools, would give a solution which is considered expensive in the area of folding box manufacture and hence economically unacceptable. Finally, it is difficult to have access to means for adjustment along the different axes on one and the same surface of the component requiring adjustment, so that the adjustment operation is rendered difficult.
The object of this invention is to obviate the above disadvantages at least partly.
To this end, the invention relates to a system for adjusting the position between a waste ejector and a cylinder for cutting material in strip form in a rotary cutting machine.
The system according to the invention has few components and is compact and economic. Its design, in which the prestressed strips connecting the two parts of the support act as a guide without any play, results in an adjustment which does not depend on any hysteresis effect and which has an excellent resolution. The system has a very good rigidity both static and dynamic in the three axes, including the axis along which the adjustment is made. Its static and dynamic torsion rigidity is high along the three axes. The adjustment components of the system have orientations directed towards the exterior of the machine which are easily accessible. The adjustment and dismantling can be effected by means of one and the same key, simplifying to the maximum the various interventions required on the machine.
Other features and advantages will be apparent from the following description of one embodiment of this system which is illustrated diagrammatically and by way of example in the accompanying drawing wherein: